Honda CB 125S


Make Model

Honda CB 125S




Four stroke, twin cylinder, OHC, 2 valve per cylinder


124 cc / 7.6 cu-in
Bore x Stroke 56.5 x 49mm
Cooling System Air cooled
Compression Ratio 9.4:1


22mm Keihin carburetors, manual choke


Battery pints 
Starting Kick

Max Power

17 hp / 12.4 kW @ 11500 rpm

Max Torque

Clutch Multi-disc, wet


5 Speed
Final Drive Chain

Front Suspension

Oil-damped telescopic forks

Rear Suspension

Swinging arm

Front Brakes


Rear Brakes


Front Tyre

2.75 -18

Rear Tyre

3.00 -18


114 kg / 252 lbs

Fuel Capacity 

9 Litres / 2.3 US gal

Road Test Cycle 1979

Long gone is the time when the major Japanese motorcycle manufacturers were battling it out in combat on the showroom floors and racetracks with 50cc and 100cc and 125cc motorcycles. The basic motorcycle went from 100 to 250 to 350 to 500 to 750ccs and with each increase there was a smaller and smaller selection of small street motorcycles.

Now, below 200cc, there is only one. The Honda CB125. It's been around since the time when all the factories had 125 street bikes. And it hasn't changed much over the years, though this year it has bright red fenders that go nicely with the tasteful styling of the little bike.

There not being any competition for the CB125, it manages to get along with the same 125cc sohc Single, five-speed transmission and combination pressed steel and tube frame. There's no electric starting or tachometer or turn signal canceler or disc brakes. This is a very basic motorcycle.

Big holes not costing any more to make than little holes, the only way Honda could sell the CB125 for less money than Yamaha does the SR500 is to leave off some of the features and cut costs wherever possible. And there just aren't that many parts on a Single that can be left off. Particularly with a sohc Single.

Of course there are no counter-rotating balancer shafts on the 125 such as those of the large Honda Singles. Nor are they needed.

On the engine is the most basic of 22mm slide valve carburetors and an ordinary battery and points ignition. This is all basic stuff, stuff that's worked for years and is easy to maintain. Valve lash is set with a screw driver and wrench. For maximum performance you shift when the speedometer needle reaches the shift mark.

Little motorcycles naturally get stigmatized. So do big motorcycles, but the stigma isn't so offensive. Little motorcycles lend themselves to beginning riders because they are light and less intimidating than bigger machines. All the controls are within the power of smaller' people, so small folks like the son who's not fully grown and the wife who can't reach the ground on the dual purpose bike can feel at home on the CB125.

Put in the right perspective, however, the 125 becomes fun (if not exciting) to those used to much bigger machines. When was the last time you were engaged in a contest of speed and didn't have to worry about getting a ticket? Heck, on the Honda 125 every stoplight is a drag race and the competition is in Honda cars and Volkswagen busses and Buick sedans. The CB125 will win those races, too, but mostly because people in cars don't drive as fast as they can. Still, there's a thrill in seeing traffic fade slowly in the rearview mirrors as the Honda is thrashed to the shift points in every gear. At least in town the traffic fades pleasantly back. Out on an open road the story is reversed as the Honda has all it can do keeping up with the flow of cars doing 60.

Because the performance is so modest, the 125 tends to be ridden flat out, all the time. People who usually refrain from such practices found themselves powershifting into second gear to pop the front wheel in the air. Other benefits of the 125 size came when traffic backed up and the 125 rider could slip between the lanes on even narrow streets.

One place the 125 isn't fun is on a busy interstate. In areas with rain grooves the grooves throw the little bike back and forth, the short handlebars wiggling disconcertingly. While the bike can reach nearly 70 mph, it can only hold 60 mph without the rider flat on the tank and without wind. Hills or headwinds can slow the bike down to 50 where it is uncomfortable in traffic. In California the 125 isn't even legal on freeways because the engine is smaller than the minimum 175cc size required. (There is no life in the slow lane in California because there's no slow lane.)

The brakes on the CB125 are worth mentioning, but that's not something positive. It's a 10 horsepower motorcycle with five horsepower brakes. One rider took the 125 to the bank and came back wanting to know what was wrong with the front brake. He didn't think it had one. At both ends of the small Honda there are tiny drum brakes, each one with 13 sq. in. of brake area. The rear brake manages to do its job because there's lots of leverage for a strong foot and the rear end of a motorcycle doesn't do much stopping anyway. Up front there's a shorter lever for a hand that's not as strong as a foot and the brake is the same size so little happens when a rider grabs the lever.

Considering this is a beginner's motorcycle, the brakes will only teach the rider that he can't pull the front brake too hard, but it could also teach the rider that it's not worth pulling it at all. Before the other factories got out of the small street bike market, Honda had a disc brake on the front of the 125. Now that there's no competition, there's the tiniest of drums.

The clutch is also marginal. It can't be held in until the signal changes because it warms up and begins to grab. When the engine is revved up before taking off the clutch can object with peculiar noises. Even during gentle riding the clutch level moves a long way, slowly taking hold, before it all-of-a-sudden grabs. Beginning riders deserve better.

Starting the 125 is simple, but not as easy as other small motorcycles have been. The lever is short and needs more pressure than a small two-stroke needs to kick it over. Once moved, the Honda starts within a couple of kicks, hot or cold. When cold, however, the choke must remain on for a few minutes or the cycle will die, but when riding the bike the choke has to be turned off so the engine will rev. Cold running could certainly be improved. Once when the Honda was kicked over it backfired and refused to start. The frustrated rider gave up and took an easy-starting Yamaha SR500 home for the night, discovering the next morning that the backfire had blown the plastic top off the 125's carburetor, taking the slide with it. The plastic carb top had simply broken in two. Another excessively cheap part.

Suspension? Yes, there is some. Again, it's what you'd put on if you couldn't sell the bike for as much as you'd like. Travel is 4.5 in. front and 2.6 in. rear, with springs stiff enough to keep a normal size person from bottoming the shocks but still able to absorb the shock from big holes. Rear spring preload is adjustable, the only adjustment on the suspension. Considering the spindly forks and tiny shocks, the suspension works better than it should.

Handling is a matter of trust. How much does the rider trust the 18 in. Bridgestone in front and the 17 in. Nitto in back? Scraping the pegs on the 125 would be a matter of bravery, not skill. Honda makes a 125 roadracer, hut this isn't it. The 47 in. wheelbase and 200 plus pounds of motorcycle make for a flighty sort of motorcycle, one that will turn instantly at the slightest provocation and the quickness increases as speed slowly builds.

The CB125 is economy transportation.

It did 78 mpg on the CR' test loop, the best result since we began doing repeatable miles-per-gallon tests. And the loop is a hit unfair to small engines, as they are working hard on the highway portions that allow superbikes to cruise with throttles barely cracked. In intended service, for example running errands, short hops to school and store, the 125 would he even better. (A minority comment here, from those who recall that the old 500 Twins, as in Triumph, used to return almost as many miles per gallon. A mild, slow-turning large engine can be as efficient as a small, high-revving engine.) But overall, the CB125 is our mpg champ to date.

One reason it's so tough to build a good small motorcycle is the amount of safety equipment required on a street bike. The reflectors and two brake light switches and signal lights and the emission certification cost as much on a small bike as on a large bike and the required equipment becomes a greater part of the motorcycle's cost.

There's a curious blend of features and lack of features on the 125. There's a helmet lock and tool box hanging below the seat on the right side. A grab strap runs across the seat. Two pods contain the speedometer/odometer in the lefthand pod and warning lights for turn signals, high beam and neutral in the righthand pod. There is no oil pressure warning light or sight gauge for checking oil level. No trip meter. The 35 watt headlight only seems to work on well lighted streets. It would be appropriate on a moped, perhaps. Yet there's a locking cover over the gas tank filler that surely requires more parts and more cost than a simple locking cap that would also be easier to use.

When Honda came up with the revised XL 125 a couple of years ago, it would have seemed natural to stick the improved 125cc engine in the CB at the same time. After all, the CDI, six-speed transmission and better carburetor cost little extra and one engine could have cut production costs. Instead, Honda changes the CB125 by adding rectangular turn signals and redesigned clutch and brake levers and hand lever dust covers and new fuel tank striping and sidecover emblems and improved seat styling.

All those changes make for a more attractive motorcycle and Honda is betting that the inexperienced rider who will buy the CB125 is more interested in the better styling than he or she would have been in improved brakes and clutch or better tires. Honda, as usual, is probably right.

Fortunately, there's also the XL125 and the almost-identical but more powerful XL185 that cost little more than the CB 125 and provide much greater performance. With a suggested retail price of $928 the CB125 is the cheapest pure street motorcycle available. It's also the best under-200cc street bike because it's the only under200cc street bike.

Source Cycle 1979